CENTRAL STATES FOREST EXPEBIME NT STATION 

 COLUMBUS, ORJ.0B. DE?T. OF ^'^■"^%'ii^JLANE, DIRECTOR 



CS-16 ^-^K i 6 i9&^ December 1963 



CURRENT SERIAL RECORDS 



ARTIFICIAL DEFOLIATION OF EASTERN WHITE PINE 



DUPLICATES SOME EFFECTS OF CHLOROTIC DWARF DISEASE 



Chlorotic dwarf is reported from all over the normal 

 range of eastern white pine (Pinus strobus L.)» The disease 

 reduces the growth and prematurely defoliates this pine. It 

 affects 3-year-old trees, those as old as 15 years, and, 

 rarely, even trees as old as 40 years. Though it has been 

 known for 50 years, its cause is still unknown. 



An attempt to duplicate some chlorotic dwarf symptoms 

 by artificially defoliating healthy white pines indicates 

 that premature shedding may be responsible for the reduced 

 growth that is customarily associated with the disease. Re- 

 moval of current needles is more likely to slow the growth of 

 shoots and even kill healthy trees outright than removal of 

 older foliage. 



Normally eastern white pine holds 3 years ' needles 

 during the summer months. After the oldest needles are 

 sloughed off in autumn, current and 1-year-old needles over- 

 winter. New needles emerge in the spring and the cycle con- 

 tinues. But trees afflicted with the chlorotic dwarf disease 

 deviate from the norm. Their failure to retain needles is 

 one of the most characteristic symptoms of this disease. In 

 all stages of tree decline, chlorotic-f lecked foliage formed 

 the preceding year falls prematurely by early summer, leaving 

 only the new needles. Few of the trees with chlorotic dwarf 

 disease die in young plantations, only 4 of 250 diseased 

 trees being lost over a 4-year period of observation. But 

 more of these disease-stunted trees may die in time because 

 of suppression by surrounding healthy trees. 



